[ruby/logger] Update lib/logger.rb

https://github.com/ruby/logger/commit/6d91281f7f

Co-authored-by: Olle Jonsson <olle.jonsson@gmail.com>

lib/logger.rb

@@ -186,7 +186,7 @@ require_relative 'logger/errors'
 #
 # === Program Name
 #
-# The program name is an optional argument to  method #add:
+# The program name is an optional argument to method #add:
 #
 #   logger = Logger.new($stdout)
 #   logger.add(Logger::INFO, 'My message', 'mung')